Benzocyclobutene-containing aromatic diamines, polyaramides, and methods of making

Abstract

The application provides a benzocyclobutene-containing aromatic diamine and a preparation method thereof, and the preparation method comprises the following steps: reacting 3-[1,4-benzenediol]-bicyclo[4.2.0]-octa-1,3,5-triene and 4-nitrochlorobenzene in a first organic solvent under alkaline conditions to obtain a benzocyclobutene-containing dinitro compound; and reducing the benzocyclobutene-containing dinitro compound in a second organic solvent under a hydrogen atmosphere to obtain a benzocyclobutene-containing aromatic diamine compound. The application also provides a benzocyclobutene-containing polyaramide polymer and a preparation method thereof. The linear polyaramide and the crosslinked polyaramide prepared by the application can adjust the content of benzocyclobutene in the structure according to the use scene, so that the mechanical strength, the thermal stability and the CTE change to adapt to different application requirements, and the linear polyaramide has good solubility in an organic solvent, so that the linear polyaramide is easy to process and has good film-forming property.

Description

Technical Field

[0001] This invention relates to the field of polyarylamide technology, specifically to an aromatic diamine containing benzocyclobutene, a polyarylamide, and a method for its preparation. Background Technology

[0002] Polyarylamides are high-performance polymers whose main chain contains at least 85% amide groups directly linked to two aromatic rings. Based on the position of the amide groups on the benzene ring, polyarylamides can be further classified into para-polyarylamides, meta-polyarylamides, and ortho-polyarylamides. These polymers are characterized by high melting point, high modulus, high strength, and radiation resistance, and are widely used in the production of high-performance synthetic fibers. In my country, polyarylamide fibers are also known as aramid fibers, and their most notable characteristics include lightweight, flame retardancy, temperature resistance, insulation, radiation resistance, high strength, and high elastic modulus; they are widely used in military defense, security protection, aerospace, environmental protection, and electronic and electrical materials.

[0003] Polyarylamide molecules contain numerous repeating polar amide groups (-CO-NH-). The amino hydrogen on these groups can combine with the carbonyl oxygen on another amide group to form a highly oriented and efficient interchain hydrogen bond network. This results in materials with a high tendency to crystallize and a high cohesive energy density, but poor solubility in organic solvents. Generally, processing is only possible after dissolving in concentrated sulfuric acid. However, concentrated sulfuric acid is highly corrosive, easily damaging processing equipment, and the polymer is easily degraded in sulfuric acid. These drawbacks significantly limit the applications of polyarylamides. Furthermore, different fields have different performance requirements for polyarylamides, and the existing performance scalability and flexibility of polyarylamides are insufficient to meet the application needs of various fields. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing an aromatic diamine containing benzocyclobutene, with the following structure: .

[0005] A method for preparing an aromatic diamine containing benzocyclobutene includes the following steps: Under nitrogen protection, 3-[1,4-benzenediol]-bicyclo[4.2.0]-oct-1,3,5-triene and 4-nitrochlorobenzene were dissolved in amide organic solvents or pyrrolidone organic solvents and then reacted under alkaline conditions to obtain a dinitro compound containing benzocyclobutene. A dinitro compound containing benzocyclobutene is dissolved in an ester-based organic solvent and then reduced under a hydrogen atmosphere to obtain an aromatic diamine compound containing benzocyclobutene.

[0006] Furthermore, the specific method for the reaction under alkaline conditions is as follows: potassium carbonate or sodium carbonate is dissolved in a first organic solvent to form alkaline conditions, the molar amount of potassium carbonate or sodium carbonate is 2-2.5 times that of 3-[1,4-benzenediol]-bicyclo[4.2.0]-octyl-1,3,5-triene, the reaction temperature is 80-130 ℃, and the reaction time is 5-10 hours.

[0007] Furthermore, the specific method for reducing the benzocyclobutene-containing dinitro compound under a hydrogen atmosphere is as follows: adding a Pd / C catalyst to the benzocyclobutene-containing dinitro compound, wherein the amount of Pd in ​​the Pd / C catalyst is 5-10‰wt of the benzocyclobutene-containing dinitro compound. The molar ratio of 3-[1,4-benzenediol]-bicyclo[4.2.0]-oct-1,3,5-triene to 4-nitrochlorobenzene is 1:2.0-2.3.

[0008] A linear polyarylamide has the following structure: x is 1-50, y is 0-49; A crosslinked polyaromatic amide has the following structure: x is 1-50, y is 0-49.

[0009] A method for preparing linear polyarylamide includes the following steps: An aromatic diamine containing benzocyclobutene, terephthalic acid, 3,4'-ODA, and CaCl2 or LiCl are added to a reaction vessel. After nitrogen purging, P(OPh)3, pyridine, and NMP are added and refluxed to obtain a linear polyarylamide.

[0010] A method for preparing crosslinked polyarylamide includes the following steps: An aromatic diamine containing benzocyclobutene, terephthalic acid, 3,4'-ODA, and CaCl2 or LiCl were added to a reaction vessel. After nitrogen purging, P(OPh)3, pyridine, and NMP were added and refluxed to obtain a linear polyarylamide. Under inert gas conditions, the linear polyarylamide is thermocured and then annealed to obtain a crosslinked polyarylamide containing a tetrahydrodibenzocyclooctadiene structure.

[0011] Furthermore, the reflux reaction conditions are 100-150 °C for 12-24 hours; the total amount of the aromatic diamine containing benzocyclobutene and 3,4'-ODA, terephthalic acid, CaCl2, P(OPh)3, and pyridine are in the molar ratio of 1:1:(2-5):(4-8):(6-12).

[0012] Furthermore, the specific method for heat curing and annealing the linear polyaramid is as follows: heat curing the linear polyaramid to 270°C for 6-10 hours, and then annealing it at 300°C for 12-20 hours.

[0013] The beneficial effects of this invention are as follows: 1. By introducing flexible segments such as ether bonds or side groups that disrupt the regularity of the molecular chain into the rigid molecular structure of polyarylamides, linear polyarylamides with good solubility can be prepared. This solves the problem of poor solubility of such materials in organic solvents.

[0014] 2. The linear polyaromatic amides and crosslinked polyaromatic amides prepared by this invention exhibit excellent mechanical strength and thermal stability. After crosslinking, the linear polyaromatic amides form a crosslinked network with a tetrahydrodibenzocyclooctadiene (DBCOD) structure between the molecular chains, which improves the polymer's thermal stability. T d 5% The average temperature increase was 36°C. T d 10% The average temperature increase was 30 °C. Benzocyclobutene's ring-opening process forms a cross-linked network, which enhances both modulus and hardness.

[0015] 3. The linear polyaromatic amides and crosslinked polyaromatic amides prepared by this invention can adjust the content of benzocyclobutene in the structure according to the application scenario, so as to change the mechanical strength, thermal stability and CTE to adapt to different application requirements.

[0016] 4. The cross-linked polyarylamide prepared by this invention has good film-forming properties, and the prepared cross-linked polyarylamide film has good flexibility and transparency, showing high processability. Attached Figure Description

[0017] Figure 1 The image shows the proton NMR spectrum of Example 4.

[0018] Figure 2 Examples 5-8 are hydrogen nuclear magnetic resonance spectra.

[0019] Figure 3 The TGA curves for the linear, cross-linked polyarylamide in Example 6 are shown.

[0020] Figure 4 The DSC curves for the linear polyaramids in Examples 4-8 are shown. Figure 5 The DSC curves for the linear, cross-linked polyarylamide in Example 4 are shown.

[0021] Figure 6 The XRD curves are for the crosslinked polyarylamides in Examples 4-8.

[0022] Figure 7 Example 7 shows the linear, cross-linked polyarylamide nanoindentation curve.

[0023] Figure 8 The TMA curves of cross-linked polyarylamide in Examples 4-8 are shown.

[0024] Figure 9 The cross-linked polyarylamide film samples are from Examples 4-8. Detailed Implementation

[0025] Unless otherwise specified, all pharmaceuticals used in the following examples are commercially available products, and all methods used are conventional methods in the art.

[0026] The present invention will be further illustrated below with reference to examples and comparative examples.

[0027] Example 1 An aromatic diamine containing benzocyclobutene, namely 3-[2,5-bis-(4-aminophenoxy)-phenyl]-bicyclo[4.2.0]-oct-1,3,5-triene, has the following structure: .

[0028] Example 2 The preparation method of the aromatic diamine containing benzocyclobutene in Example 1 includes the following steps: Step (1): Preparation of 3-[2,5-bis-(4-nitrophenoxy)-phenyl]-bicyclo[4.2.0]-oct-1,3,5-triene: Weigh 2.122 g (10 mmol) of 3-[1,4-benzenediol]-bicyclo[4.2.0]-oct-1,3,5-triene, 3.307 g (21 mmol) of 4-nitrochlorobenzene, and 3.040 g (22 mmol) of anhydrous K2CO3 into a 250 mL single-necked flask, and then add 30 mL of DMF. The mixture is placed under nitrogen atmosphere and heated to 120 °C for 8 hours. After the reaction was completed, 100 mL of deionized water was added, and a black solid precipitated out. The aqueous phase was extracted three times with 30 mL of ethyl acetate. The organic phases were combined, dried with anhydrous sodium sulfate, filtered and concentrated, and then subjected to column chromatography with petroleum ether-ethyl acetate to obtain 4.15 g of the compound, with a yield of 92%.

[0029] Step (2): Preparation of 3-[2,5-bis-(4-aminophenoxy)-phenyl]-bicyclo[4.2.0]-oct-1,3,5-triene: Weigh 4.521 g (10 mmol) of 3-[2,5-bis-(4-nitrophenoxy)-phenyl]-bicyclo[4.2.0]-oct-1,3,5-triene and add 150 mL of ethyl acetate to a 250 mL three-necked flask. After purging with nitrogen, add 1.36 g of 5% palladium-on-carbon catalyst to the three-necked flask and purge with hydrogen. React for 48 hours. After the reaction is complete, purge with nitrogen, filter the palladium-on-carbon catalyst, concentrate it, and obtain 3.55 g of pure 3-[2,5-bis-(4-nitrophenoxy)-phenyl]-bicyclo[4.2.0]-oct-1,3,5-triene by column chromatography in petroleum ether-ethyl acetate, yielding 90%.

[0030] The aromatic diamine compound 3-[2,5-bis-(4-aminophenoxy)-phenyl]-bicyclo[4.2.0]-oct-1,3,5-triene was finally obtained, and its 1H NMR spectrum, infrared spectrum, mass spectrometry, and melting point data are as follows: 1 H NMR (400 MHz, DMSO- d 6): δ 12.82 (s, 1H), 7.98 (d, J = 8.1 Hz, 2H), 7.87 (d, J = 8.0 Hz, 2H), 7.28 (d, J = 7.6 Hz, 1H), 7.24-7.13 (m, 6H), 7.06(d, J = 7.6 Hz, 1H), 6.95 (d, J = 8.2 Hz, 2H), 3.09 (s, 4H). FT-IR: ν = 3072,2928, 1681, 1600, 1493, 1467, 1225, 1163, 935, 858 cm -1 ESI-MS: 394 [MH] - HRMS: [MH] - calcd for C 26 H 22 N2O2 - , 394.1681, found 394.1765. Mp: 88.5-93.1 ℃ (ethyl acetate). Example 3 The structure of the benzocyclobutene-containing polyaromatic amide polymer prepared from an aromatic diamine containing benzocyclobutene is as follows: The structural formula of the linear polyarylamide containing benzocyclobutene is as follows: x is 1-50, y is 0-49; The structural formula of the crosslinked polyarylamide containing a tetrahydrodibenzocyclooctadiene structure is as follows: x is 1-50, y is 0-49.

[0031] Example 4 A method for preparing the benzocyclobutene-containing polyaromatic amide polymer prepared from the aromatic diamine containing benzocyclobutene in Example 3 specifically includes the following steps: 3-[2,5-bis-(4-aminophenoxy)-phenyl]-bicyclo[4.2.0]-oct-1,3,5-triene (394 mg, 1.0 mmol), terephthalic acid (TPA) (166 mg, 1.0 mmol), and CaCl2 (222 mg, 2.0 mmol) were added to a 25 mL Schlenk tube. After nitrogen purging, P(OPh)3 (1.0 mL), pyridine (0.5 mL), and NMP (2 mL) were mixed and added to the Schlenk tube using a syringe. The reaction system was heated to 120 °C and stirred thoroughly. After reacting for 24 hours, the reaction solution was cooled to room temperature, and 50 mL of methanol was added to cause polymer coagulation. The precipitate was collected by centrifugation and washed thoroughly with methanol. The polymer was dried under vacuum at 40 °C to obtain 513 mg of linear polyarylamide, with a yield of 98%, and the structure is as follows: x=20, y=0. 1 H NMR (400 MHz, DMSO- d 6): δ 10.4 (s, 1H), 10.4 (s, 1H), 8.1 (t, J =6.1 Hz, 4H), 7.8 (d, J = 8.0 Hz, 2H), 7.7 (d, J = 8.4 Hz, 2H), 7.3 (d, J =7.5 Hz, 2H), 7.2 (s, 2H), 7.1 (dd, J = 23.0, 7.8 Hz, 5H), 7.0 (s, 3H), 6.9(d, J= 8.2 Hz (2H), 3.1 (s, 4H). The preparation method of crosslinked polyarylamide involves fully dissolving linear polyarylamide in NMP to prepare a 40 mg / mL polymer solution, which is then dropped onto a clean substrate. After the solvent evaporates, the solution is dried at 110 °C for 10 hours. The film is then peeled off from the substrate to obtain a self-supporting film. This film is then thermocured at 270 °C for 6 hours under nitrogen atmosphere and annealed at 300 °C for 10 hours. After cooling, the crosslinked polyarylamide is obtained.

[0032] Example 5 A method for preparing the benzocyclobutene-containing polyaromatic amide polymer prepared from the aromatic diamine containing benzocyclobutene in Example 3 specifically includes the following steps: 3-[2,5-bis-(4-aminophenoxy)-phenyl]-bicyclo[4.2.0]-octyl-1,3,5-triene (197 mg, 0.6 mmol), 3,4'-ODA (60 mg, 0.3 mmol), TPA (149 mg, 0.9 mmol), and CaCl2 (222 mg, 2.0 mmol) were added to a 25 mL Schlenk tube. After nitrogen purging, P(OPh)3 (1.0 mL), pyridine (0.5 mL), and NMP (2 mL) were mixed and added to the Schlenk tube using a syringe. The reaction system was heated to 120 °C and stirred thoroughly. After reacting for 24 hours, the reaction solution was cooled to room temperature, and 50 mL of methanol was added to cause polymer coagulation. The precipitate was collected by centrifugation and washed thoroughly with methanol. The polymer was dried under vacuum at 40 °C to obtain 419 mg of linear polyarylamide, with a yield of 99%, and the structure is as follows: x=23, y=10. 1 H NMR (400 MHz, DMSO- d 6): δ 10.5 (s, 2H), 10.4 (s, 1H), 8.1 (t, J =7.6 Hz, 6H), 7.9-7.8 (m, 3H), 7.7 (d, J = 7.8 Hz, 2H), 7.6 (d, J = 13.1 Hz,1H), 7.4-7.3 (m, 3H), 7.2 (s, 2H), 7.2-7.0 (m, 9H), 6.9 (d, J = 8.0 Hz, 2H), 6.8 (d, J= 7.4 Hz, 1H), 3.1 (s, 4H). The preparation method of crosslinked polyarylamide involves fully dissolving linear polyarylamide in NMP to prepare a 40 mg / mL polymer solution, which is then dropped onto a clean substrate. After the solvent evaporates, the solution is dried at 110 °C for 10 hours. The film is then peeled off from the substrate to obtain a self-supporting film. This film is then thermocured at 270 °C for 6 hours under nitrogen atmosphere and annealed at 300 °C for 10 hours. After cooling, the crosslinked polyarylamide is obtained.

[0033] Example 6 A method for preparing the benzocyclobutene-containing polyaromatic amide polymer prepared from the aromatic diamine containing benzocyclobutene in Example 3 specifically includes the following steps: 3-[2,5-bis-(4-aminophenoxy)-phenyl]-bicyclo[4.2.0]-octyl-1,3,5-triene (197 mg, 0.5 mmol), 3,4'-ODA (100 mg, 0.5 mmol), TPA (166 mg, 1.0 mmol), and CaCl2 (222 mg, 2.0 mmol) were added to a 25 mL Schlenk tube. After nitrogen purging, P(OPh)3 (1.0 mL), pyridine (0.5 mL), and NMP (2 mL) were mixed and added to the Schlenk tube using a syringe. The reaction system was heated to 120 °C and stirred thoroughly. After reacting for 24 hours, the reaction solution was cooled to room temperature, and 50 mL of methanol was added to cause polymer coagulation. The precipitate was collected by centrifugation and washed thoroughly with methanol. The polymer was dried under vacuum at 40 °C to obtain 383 mg of linear polyarylamide, with a yield of 98%, and the structure is as follows: x=25, y=25. 1 H NMR (400 MHz, DMSO- d 6): δ 10.5 (s, 3H), 10.4 (s, 1H), 8.1 (t, J =9.0 Hz, 8H), 7.8 (s, 4H), 7.7 (d, J = 7.9 Hz, 2H), 7.6 (d, J = 10.9 Hz, 2H),7.4-7.3 (m, 3H), 7.2 (s, 2H), 7.2-7.0 (m, 10H), 6.9 (d, J = 7.8 Hz, 4H), 6.8 (d, J= 7.4 Hz, 1H), 3.1 (s, 4H). The preparation method of crosslinked polyarylamide involves fully dissolving linear polyarylamide in NMP to prepare a 40 mg / mL polymer solution, which is then dropped onto a clean substrate. After the solvent evaporates, the solution is dried at 110 °C for 10 hours. The film is then peeled off from the substrate to obtain a self-supporting film. This film is then thermocured at 270 °C for 6 hours under nitrogen atmosphere and annealed at 300 °C for 10 hours. After cooling, the crosslinked polyarylamide is obtained.

[0034] Example 7 A method for preparing the benzocyclobutene-containing polyaromatic amide polymer prepared from the aromatic diamine containing benzocyclobutene in Example 3 specifically includes the following steps: 3-[2,5-bis-(4-aminophenoxy)-phenyl]-bicyclo[4.2.0]-octyl-1,3,5-triene (118 mg, 0.3 mmol), 3,4'-ODA (120 mg, 0.6 mmol), TPA (149 mg, 0.9 mmol), and CaCl2 (222 mg, 2.0 mmol) were added to a 25 mL Schlenk tube. After nitrogen purging, P(OPh)3 (1.0 mL), pyridine (0.5 mL), and NMP (2 mL) were mixed and added to the Schlenk tube using a syringe. The reaction system was heated to 120 °C and stirred thoroughly. After reacting for 24 hours, the reaction solution was cooled to room temperature, and 50 mL of methanol was added to cause polymer coagulation. The precipitate was collected by centrifugation and washed thoroughly with methanol. The polymer was dried under vacuum at 40 °C to obtain 341 mg of linear polyarylamide, with a yield of 95%, and its structure is as follows: x=11, y=18. 1 H NMR (400 MHz, DMSO- d 6): δ 10.5 (s, 2H), 10.4 (s, 1H), 8.1 (t, J =10.4 Hz, 6H), 7.8 (s, 3H), 7.7 (d, J = 6.4 Hz, 1H), 7.6 (d, J = 8.9 Hz, 2H),7.5-7.3 (m, 2H), 7.2 (s, 1H), 7.1 (q, J = 10.6, 7.8 Hz, 4H), 7.0 (s, 2H), 6.9(d, J= 8.0 Hz, 1H), 6.8 (d, J = 7.1 Hz, 1H), 3.1 (s, 2H). The preparation method of crosslinked polyarylamide involves fully dissolving linear polyarylamide in NMP to prepare a 40 mg / mL polymer solution, which is then dropped onto a clean substrate. After the solvent evaporates, the solution is dried at 110 °C for 10 hours. The film is then peeled off from the substrate to obtain a self-supporting film. This film is then thermocured at 270 °C for 6 hours under nitrogen atmosphere and annealed at 300 °C for 10 hours. After cooling, the crosslinked polyarylamide is obtained.

[0035] Example 8 A method for preparing the benzocyclobutene-containing polyaromatic amide polymer prepared from the aromatic diamine containing benzocyclobutene in Example 3 specifically includes the following steps: 3-[2,5-bis-(4-aminophenoxy)-phenyl]-bicyclo[4.2.0]-octyl-1,3,5-triene (39 mg, 0.1 mmol), 3,4'-ODA (180 mg, 0.9 mmol), TPA (166 mg, 1.0 mmol), and CaCl2 (222 mg, 2.0 mmol) were added to a 25 mL Schlenk tube. After nitrogen purging, P(OPh)3 (1.0 mL), pyridine (0.5 mL), and NMP (2 mL) were mixed and added to the Schlenk tube using a syringe. The reaction system was heated to 120 °C and stirred thoroughly. After reacting for 24 hours, the reaction solution was cooled to room temperature, and 50 mL of methanol was added to cause polymer coagulation. The precipitate was collected by centrifugation and washed thoroughly with methanol. The polymer was dried under vacuum at 40 °C to obtain 317 mg of linear polyarylamide, with a yield of 96%, and the structure is as follows: x=6, y=40. 1 H NMR (400 MHz, DMSO- d 6): δ 10.5 (s, 2H), 10.4 (s, 0.1H), 8.1 (t, J =11.1 Hz, 4H), 7.8 (s, 2H), 7.7 (d, J = 9.3 Hz, 0.3H), 7.6 (s, 2H), 7.4 (t, J = 7.1 Hz, 1H), 7.2-6.9 (m, 4H), 6.8-6.7 (m, 1H), 3.1 (s, 0.4H). The preparation method of crosslinked polyarylamide involves fully dissolving linear polyarylamide in NMP to prepare a 40 mg / mL polymer solution, which is then dropped onto a clean substrate. After the solvent evaporates, the solution is dried at 110 °C for 10 hours. The film is then peeled off from the substrate to obtain a self-supporting film. This film is then thermocured at 270 °C for 6 hours under nitrogen atmosphere and annealed at 300 °C for 10 hours. After cooling, the crosslinked polyarylamide is obtained.

[0036] Performance testing: The specific synthetic route for aromatic diamines containing benzocyclobutene is shown in the following formula: The 3-[2,5-bis-(4-aminophenoxy)-phenyl]-bicyclo[4.2.0]-oct-1,3,5-triene obtained in Example 2 was subjected to nuclear magnetic resonance (NMR) testing, as shown... Figure 1 As shown.

[0037] Nuclear magnetic resonance (NMR) tests were performed on the linear polyarylamides obtained in Examples 4-8, such as... Figure 2 As shown. The content of benzocyclobutene structural units in polyarylamides can be calculated by integrating the characteristic peak signal (3.12 ppm) of the aliphatic region of benzocyclobutene in the proton NMR spectrum based on the molar ratio of 3-[2,5-bis-(4-aminophenoxy)-phenyl]-bicyclo[4.2.0]-oct-1,3,5-triene / 3,4'-ODA / TPA. Since the cross-linked polyarylamides are insoluble, no NMR data were obtained. This is because introducing flexible segments such as ether bonds or side groups that disrupt the regularity of the molecular chain into the rigid linear polyarylamide molecular structure can prepare polyarylamides with good solubility and thermal stability.

[0038] The linear and crosslinked polyarylamides obtained in Examples 4-8 were subjected to TGA testing, and the results are shown in Table 1. The linear polyarylamides were measured to have... T d 5% The window temperature is 378-403 ℃. T d 10% The temperature window is 452-467 ℃; cross-linked polyarylamide T d 5% The window temperature is 421-442 ℃. T d 10% The temperature window is 487-489 °C. After crosslinking, this linear polyarylamide forms a crosslinked network with a tetrahydrodibenzocyclooctadiene (DBCOD) structure between the molecular chains, which improves the polymer's thermal stability. T d 5%The average temperature increase was 36°C. T d 10% The average temperature increase was 30 °C. Example 4: Comparison of linear and cross-linked polyarylamides is shown in the figure. Figure 3 As shown.

[0039] Table 1. Molar ratio of benzocyclobutene in linear polyarylamides for each example's thermogravimetric temperature series. The linear, crosslinked polyarylamides obtained in Examples 4-8 were subjected to DSC testing, and the results are as follows: Figure 4 and Figure 5 As shown in the figure. The thermosetting behavior of a series of linear polyarylamides containing benzocyclobutene can be clearly seen through DSC curves, thus determining the temperature parameters for preparing crosslinked polyarylamides. Their [4+4] ring-opening temperatures are 274-294 ℃. No glass transition temperature was observed in this series of linear and crosslinked polyarylamides.

[0040] XRD tests were performed on the crosslinked polyarylamides obtained in Examples 4-8, and the results are as follows: Figure 6 As shown, only the peak intensity of the polyarylamide decreased before and after crosslinking; its amorphous morphology remained unchanged. All crosslinked polyarylamides exhibited broad peaks, indicating an amorphous morphology. This is attributed to the introduction of more ether bonds and the asymmetric monomer 3,4'-ODA, which reduces the rigidity and regularity of the molecular chains, disrupts the close packing of polymer chains, and causes the macromolecules to change from straight chains to coiled structures. This alters the aggregated structure within the polymer, leading to a decrease in crystallinity. Simultaneously, the crosslinking network formed between molecular chains increases the free volume of the polymer. These effects significantly reduce the crystallinity of the polymer.

[0041] The linear, cross-linked polyarylamides obtained in Examples 4-8 were subjected to nanoindentation tests, with an application of 50... μ A force of N was applied to a sample with dimensions of 25 × 25 mm and a thickness of 22 ± 2 mm. μThe results are shown in Table 2. The changes in hardness and Young's modulus of the series of polyarylamides before and after crosslinking were measured. The Young's modulus of linear polyarylamides ranged from 4.13 to 7.56 GPa, and the hardness ranged from 0.21 to 0.63 GPa; the Young's modulus of crosslinked polyarylamides ranged from 6.48 to 7.46 GPa, and the hardness ranged from 0.21 to 0.65 GPa. Example 4 was a binary polymer with high regularity; the ring-opening of benzocyclobutene formed a crosslinking network, which enhanced the modulus and hardness. The mechanical properties of Examples 5-7 showed that the modulus and hardness of the series of linear polyarylamides were greater than those of the series of crosslinked polyarylamides. This was attributed to the crosslinking network formed by the ring-opening of benzocyclobutene disrupting the hydrogen bonds between molecular chains, leading to a decrease in Young's modulus and hardness. In Example 8, the third monomer, 3,4'-ODA, had a large proportion and its molecular rigidity was lower than that of the benzocyclobutene structure, resulting in a decrease in the molecular strength of the linear polymer. The formation of the crosslinking network enhanced the mechanical properties of the polymer, and all Young's moduli and hardness were improved. Figure 7 The loading and unloading curves of the nanoindenter before and after crosslinking in Example 7 are shown.

[0042] Table 2 Young's modulus and hardness of each embodiment The crosslinked polyaramids obtained in Examples 4-8 were subjected to TMA testing using a tensile mode at temperatures ranging from 25 to 200 °C. The results are as follows: Figure 8 As shown, the CTE (25-150 °C) for Examples 6 and 7 are -1.2 and -11.0 × 10⁻⁶, respectively. -6 K -1 A negative value indicates the presence of a thermal shrinkage effect. The CTE (25-150 °C) for the series of cross-linked polyarylamide samples (except Example 7) was -1.2 to 4.3 × 10⁻⁶. -6 K -1 With a coefficient of thermal expansion close to zero, it has potential applications in many fields where dimensional accuracy is critical; the CTE (25-200 ℃) is 15.1-17.9 × 10⁻⁶. -6 K -1 With a CTE value close to that of Cu, it has potential applications in optics, energy, and microelectronics. In summary, the CTE window of this series of crosslinked polyarylamides ranges from -11.0 to 17.9 × 10⁻⁶. -6 K -1 This material, with its low CTE and wide deformation window, is suitable for specific applications. It exhibits a deformation rate of -1.37 to 3.12‰ and good dimensional stability. Specific data are shown in Table 3.

[0043] Table 3. CTE and deformation rate of crosslinked polyarylamides in each example This series of polyaramids exhibits good film-forming properties, and the polyaramid films demonstrate excellent flexibility and transparency. Samples of the series of cross-linked polyaramid films are shown below. Figure 9 As shown.

[0044] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A linear polyarylamide, characterized in that: An aromatic diamine containing benzocyclobutene, terephthalic acid, 3,4'-ODA, and CaCl2 or LiCl were added to a reaction vessel. After purging with nitrogen, P(OPh)3, pyridine, and NMP were added and refluxed to obtain a linear polyarylamide. The structure of the linear polyarylamide is as follows: x is 1-50, y is 0-49 and not equal to 0; The structure of the aromatic diamine of benzocyclobutene is as follows: ； The total amount of benzocyclobutene-containing aromatic diamine and 3,4'-ODA, terephthalic acid, CaCl2, P(OPh)3, and pyridine in the molar ratio is 1:1:(2-5):(4-8):(6-12).

2. The linear polyaramid according to claim 1, characterized in that: The reflux reaction is carried out at 100-150°C for 12-24 hours.

3. The linear polyaramid according to claim 1, characterized in that, The method for preparing the aromatic diamine containing benzocyclobutene is as follows: Under nitrogen protection, 3-[1,4-benzenediol]-bicyclo[4.2.0]-oct-1,3,5-triene and 4-nitrochlorobenzene were dissolved in amide or pyrrolidone organic solvents and reacted under alkaline conditions to obtain a dinitro compound containing benzocyclobutene. The structure of 3-[1,4-benzenediol]-bicyclo[4.2.0]-oct-1,3,5-triene is as follows: ; A dinitro compound containing benzocyclobutene is dissolved in an ester-based organic solvent and then reduced under a hydrogen atmosphere to obtain an aromatic diamine compound containing benzocyclobutene.

4. The linear polyarylamide according to claim 3, characterized in that, The specific method for the reaction under alkaline conditions is as follows: potassium carbonate or sodium carbonate is dissolved in an organic solvent to form alkaline conditions. The molar amount of potassium carbonate or sodium carbonate is 2-2.5 times that of 3-[1,4-benzenediol]-bicyclo[4.2.0]-octyl-1,3,5-triene. The reaction temperature is 80-130℃ and the reaction time is 5-10 hours.

5. The linear polyarylamide according to claim 3, characterized in that, The specific method for reducing the benzocyclobutene-containing dinitro compound under a hydrogen atmosphere is as follows: Pd / C catalyst is added to the benzocyclobutene-containing dinitro compound, and the amount of Pd in ​​the Pd / C catalyst is 5-10‰wt of the benzocyclobutene-containing dinitro compound. The molar ratio of 3-[1,4-benzenediol]-bicyclo[4.2.0]-oct-1,3,5-triene to 4-nitrochlorobenzene is 1:2.0-2.

3.

6. The crosslinked polyarylamide prepared according to claim 1, characterized in that: Under inert gas conditions, the linear polyarylamide was thermocured and then annealed to obtain a crosslinked polyarylamide containing a tetrahydrodibenzocyclooctadiene structure, with the following structure: x is 1-50, y is 0-49 and not equal to 0.

7. The crosslinked polyaromatic amide according to claim 6, characterized in that, The specific method for annealing the linear polyaramid after thermosetting is as follows: The linear polyaramid is thermocured at 270°C for 6-10 hours and then annealed at 300°C for 12-20 hours.

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